Remove the -d and -D options of pg_dump and pg_dumpall. The functionality
is still available, but you must now write the long equivalent --inserts
or --column-inserts. This change is made to eliminate confusion with the
use of -d to specify a database name in most other Postgres client programs.
Original patch by Greg Mullane, modified per subsequent discussion.

This is great news. One less way a new user of pg (or one that doesn't read –help pages) can do himself harm, one less thing that is purely illogical.